Microphone

ABSTRACT

A microphone includes a voice coil, a membrane and a diaphragm that has an annular convex portion encircling a central convex portion and a concentric cutout portion on the central convex portion. The membrane covers the cutout portion and extends to the periphery of the central convex portion. The combination of a properly designed cutout portion, the thickness of the membrane, the materials used for the membrane and the diaphragm, and the adhesive method employed to connect the membrane and the diaphragm shall result in a microphone that is capable of delivering high quality sound.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a microphone, more specifically to a microphonewith an improved diaphragm that increases the sensitivity andresponsiveness of the microphone.

2. Description of the Related Art

Microphones can be divided into several categories depending on thetransducer principle used. The dynamic microphone is a popularconventional microphone and comprises a magnet which has opposite polesand which is mounted inside a housing, a voice coil which is disposedmovably in a magnetic field between the opposite poles of the magnet,and a diaphragm which is attached to the upper end of the voice coil andwhich is spread over the cross section of the housing.

In the dynamic microphone, the compression and rarefaction of soundwaves actuate the diaphragm, thus causing movements in the attachedvoice coil and creating a varying magnetic flux. This varying flux,together with the magnetic field generated by the magnet, produceselectrical signals which are provided to an amplifier and then to aspeaker.

FIG. 1 shows a light and flexible conventional diaphragm 10 thatcomprises a central convex portion 11, an annular convex portion 12encircling the central convex portion 11, the juncture of the convexportions 11, 12 being attached to a voice coil 13 located below, aplurality of ribs 14 on the surface of the annular convex portion 12,and a flat periphery 15. Different portions of the diaphragm 10 respondto different frequency ranges. The central convex portion 11 responds toa high frequency range, the ribs 14 respond to a mid-frequency range,and the annular convex portion 12 responds to a low frequency range. Thequality of the broadcast sound depends upon the flexibility andlightness of the components. In a high quality microphone, the highfrequency range responding component is rigid and light, while the lowfrequency range responding component is flexible. However, all of thecomponents of the conventional diaphragm 10 are made of the samematerial. They all have the same thickness and rigidity. Thus, amicrophone which uses the diaphragm 10 is unable to deliver high qualitysounds.

Another type of conventional diaphragm 20, as shown in FIG. 2, comprisesa flat periphery 213, an annular convex portion 212, a central convexportion 211, and a membrane 22 of equivalent size as the central convexportion 211 and covering the central convex portion 211. The addition ofthe membrane 22 increases the rigidity required in the high frequencyrange. However, the membrane 22 is attached back-to-back with thecentral convex portion 211 by an adhesive. Such adhering methodincreases the weight of the diaphragm 20, thereby resulting in anadverse effect on the sound quality.

SUMMARY OF THE INVENTION

Therefore, the object of this invention is to provide a microphone withan improved diaphragm that permits the production of high quality sound.

Accordingly, the microphone of the present invention comprises a housinghaving an opening on an upper end thereof, a magnet with opposite polesmounted inside the opening, a voice coil disposed movably in a magneticfield generated between the opposite poles of the magnet, a diaphragmattached to the voice coil, and a membrane. The membrane covers thediaphragm, and is attached to a peripheral edge of the diaphragm. Thediaphragm has a central convex portion dimensionally matching theperimeter of the voice coil, a concentric cutout portion on an apex ofthe central convex portion, and an annular convex portion encircling thecentral convex portion and forming an annular juncture. The annularjuncture is attached to the voice coil at an upper circumferential endof the voice coil so the voice coil will move in the magnetic field byvirtue of movement of the diaphragm in response to compression andrarefaction of sound waves.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the present invention will becomeapparent in the following detailed description of the preferredembodiment with reference to the accompanying drawings, of which:

FIG. 1 is a perspective view of a first type of conventional diaphragmused in a microphone;

FIG. 2 is a sectional view showing another type of conventionaldiaphragm used in a microphone;

FIG. 3 is a schematic sectional view of the preferred embodiment of amicrophone according to the present invention;

FIG. 4 is an exploded perspective view of the diaphragm of the preferredembodiment; and

FIG. 5 is a sectional view showing the diaphragm of the preferredembodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 3, the preferred embodiment of a microphone of thepresent invention is shown to comprise a housing 60, a magnet 61 mountedinside an opening formed on an upper end of the housing 60, a voice coil50 disposed movably in a magnetic field generated between opposite polesof the magnet 61, a diaphragm 30 spread over the cross section of thehousing 60 and attached to the upper end of the housing 60 at theperiphery 35 thereof, the diaphragm 30 being further attached to the topof the voice coil 50, and a membrane 40 covering the central convexportion 31 of the diaphragm 30.

FIG. 4 and 5 show the diaphragm 30, the membrane 40 and the voice coil50 in greater detail. The diaphragm 30 has an annular convex portion 33that encircles a central convex portion 31, a concentric cutout portion32 on an apex of the central convex portion 31, and a plurality of ribs34 on the surface of the annular convex portion 33. The cutout portion32 compensates for the weight of the membrane 40 that is applied to thediaphragm 30. Thus, the size of the cutout portion 32 depends upon thematerials used for the diaphragm 30 and the membrane 40, and the degreeof desired high frequency sensitivity.

The membrane 40, which is equivalent in size as the central convexportion 31, covers the cutout portion 32 and extends to a peripheraledge of the central convex portion 31. The membrane 40 is made of arigid yet light material, such as Mylar or an aluminum alloy, and itsthickness is determined by the desired responsiveness to the highfrequency range.

A juncture 36 between the central convex portion 31 and the annularconvex portion 33 is attached to the top periphery of the voice coil 50.The membrane 40 has a periphery 41 which is also connected to thecentral convex portion 31 at the juncture 36 by known adhesive methods.

In order for the microphone to deliver high quality sound, the centralconvex portion 31 of the diaphragm 30 is covered by the membrane 40,which has a predesignated thickness and which is made of a more rigidbut lighter material than the diaphragm 30. The central convex portion31 thus meets the rigid and light requirements of the high frequencyrange, while the encircling annular convex portion 33 retains theflexibility that is needed at the low frequency range. Such designenables the diaphragm 30 to be highly responsive to all frequencyranges. Moreover, the membrane 40 and the diaphragm 30 are connectedonly at the juncture 36. Thus, the addition of the membrane 40 increasesthe rigidity of the central convex portion 31 but will not greatlyincrease the weight applied on the diaphragm 30 due to theaforementioned connection. Furthermore, the size of the cutout portion32 of the diaphragm 30 also serves to compensate for the increase inweight due to the presence of the membrane 40.

While the present invention has been described in connection with whatis considered the most practical and preferred embodiment, it isunderstood that this invention is not limited to the disclosedembodiment but is intended to cover various arrangements included withinthe spirit and scope of the broadest interpretation so as to encompassall such modifications and equivalent arrangements.

I claim:
 1. A microphone comprising:a housing having an opening on anupper end thereof; a magnet mounted inside said opening and having twoopposite poles, said magnet generating a magnetic field between saidopposite poles; a voice coil disposed movably in said magnetic field; adiaphragm spread over said opening and attached to said upper end ofsaid housing at a peripheral portion thereof, said diaphragm having acentral convex portion dimensionally matching perimeter of said voicecoil, said central convex portion having a concentric cutout portion,said diaphragm further having an annular convex portion encircling saidcentral convex portion and forming an annular juncture with said centralconvex portion, said annular juncture being attached to said voice coilso that said voice coil will move in said magnetic field by virtue ofmovement of said diaphragm in response to compression and rarefaction ofsound waves; and a membrane made of a material more rigid than saiddiaphragm, said membrane covering said cutout portion and extending tosaid annular juncture, said membrane being connected to said centralconvex portion only at said annular juncture.
 2. A microphone as claimedin claim 1, wherein said membrane is made of Mylar.
 3. A microphone asclaimed in claim 1, wherein said membrane is made of an aluminum alloy.4. A microphone as claimed in claim 1, wherein said annular convexportion has a plurality of ribs located on a surface thereof.